Task #390: Always play notification sounds (foreground + background)

Removed the `document.visibilityState === "visible"` early-return from
two playback paths so notification sounds fire even when the Tx OS tab
is the active foreground tab:

- `use-notifications-socket.ts` — order + meeting socket events.
- `upcoming-meeting-alert.tsx` — 5-min upcoming-meeting alert chime.

All other gates remain unchanged: global mute, per-channel sound and
vibration toggles, the ~600ms throttle in the audio player, and the
per-meeting `playedRef` dedupe by `meetingId`.

Verified `pnpm --filter @workspace/tx-os typecheck` passes.

artifacts/tx-os/src/components/executive-meetings/upcoming-meeting-alert.tsx

@@ -460,15 +460,14 @@ export function UpcomingMeetingAlert() {
 
   // Play the meeting reminder sound exactly once per *new* eligible
   // meeting (deduped by id) so polling refetches don't replay the chime
-  // every 30s. Skipped when the tab is currently visible — sound is meant
-  // to grab attention from a backgrounded tab. Honors mute and the
+  // every 30s. Plays whether the tab is foreground or background — the
+  // user wants to hear the reminder either way. Honors mute and the
   // per-channel meeting toggle.
   const playedRef = useRef<Set<number>>(new Set());
   useEffect(() => {
     if (!eligibleId || !user) return;
     if (playedRef.current.has(eligibleId)) return;
     playedRef.current.add(eligibleId);
-    if (typeof document !== "undefined" && document.visibilityState === "visible") return;
     if (user.notificationsMuted) return;
     if (!user.notifyMeetingsEnabled) return;
     notificationPlayer.play(user.notificationSoundMeeting, {

artifacts/tx-os/src/hooks/use-notifications-socket.ts

@@ -42,11 +42,10 @@ export function useNotificationsSocket() {
         });
       }
 
-      // Per-user sound + vibration. Stay silent when the tab is in the
-      // foreground (the visible UI already conveys the change), when the
-      // user has globally muted notifications, or when this event type
-      // is opted-out.
-      if (typeof document !== "undefined" && document.visibilityState === "visible") return;
+      // Per-user sound + vibration. Plays whether the tab is in the
+      // foreground or background — users want to hear the chime even
+      // while looking at the app. Still silenced by global mute and
+      // per-channel opt-outs below.
       if (user.notificationsMuted) return;
       const isOrder = payload?.type === "order";
       const isMeeting = payload?.type === "executive_meeting";